Catching Rays: Building the Water Tanks

The low-resolution water tank model is made of two polygon meshes, one for the cylindrical water tank, and one for the dome.

The water tanks and other observatory structures will be built in Maya. We’ll make two versions of the water tank – a low-poly version to be inserted into the Terragen scene, and a high-resolution version for a detailed cutaway.

The low-poly is quick work, with a simple cylinder for the body and a section of a sphere for the dome. The real domes are made of fabric stretched over frames, so extra edges are added to simulate shape of the frames.

Probably more detail than we need, but then again I’m not sure how close the camera will need to be. I’d rather not to have to rebuild anything.

Copies of the low-resolution water tank are set in place and other structures are added.

The low-poly tank is duplicated to create more than 300 tanks, and these are arranged using a satellite image of the observatory as a guide. Other buildings and a retaining wall are added.

A low-res rendering of the water tanks and other structures.

Here is a quick test rendering. So far, so good.

HAWC observatory water tanks, data center, offices, outbuildings, and a retaining wall are placed in the Terragen scene.

The shaded models are dropped into the scene. All of the pieces have been built to scale, so I know they should fit together. Still, it’s always a relief when they do.

A spherical rendering captured by a camera placed in the center of the water tank array.

Now we’ll position a spherical camera in the center of the tank array and use it to render a 360-degree view. The result is a 32-bit high dynamic range image that we’ll use to illuminate the high-resolution water tank model.

The NURBS water tank model is made of four surfaces – the tank itself, dome, liner, and water cylinder.

That model is also built in Maya, but instead of polygon meshes it will be made of NURBS surfaces. You can thing of NURBS as infinitely flexible, square sheets of thin metal or plastic that can be reshaped into almost any geometric or organic form. They are more challenging to work with than poly meshes, but the results can be much smoother when viewed at any distance. (If you are a graphic designer, think of poly meshes as bitmap images, and NURBS as vector images. Same idea.) Artificial structures, like this water tank, are perfect subjects for NURBS.

The high-resolution model, shaded and lit, viewed in Maya. The spherical image that we rendered earlier is projected onto the background and will be our primary light source for the final rendering.

The four surfaces – steel tank, dome, plastic tank liner, and water cylinder – are shaded and lit. The main source of illumination will be the HDR image that we rendered earlier. A technique called image-based lighting is used to turn it into an environment that surrounds and illuminates the model. The main benefit here is that it will also create nice, realistic reflections on the surface of the steel tank.

A soft light behind and to the left of the camera provides fill light, and a spotlight placed below the dome inside the tank highlights the tank floor and four photomultiplier tubes.

The final image is rendered out in several passes as a 32-bit image. The passes – each of which records a specific type of light such as diffuse, reflective, or refractive – are combined and adjusted in Photoshop.

The high-resolution water tank, rendered and ready for placement in the graphic.

The result is converted to an 8-bit file, ready to be placed in the final graphic.